On her return, Yadav said she had taken her first steps to get into higher honours.
The 13-year-old Bombay Cambridge school girl, the lone Indian competitor picked by the Indian Triathlon Federation, clocked 44 minutes and 26 seconds in the event comprising a 350m swim, 9.7km cycling and 3.5km running, a media release said today.
15-year-old Zoe Bowden of Malaysia won the gold in 40:24 and Magali Bernasconi Echauz of the host nation won silver in 42:40.
Victorija Astor Deldio, also of the Philippines, was third in 43:18. Swapnali was beaten to the sixth place in a close fight with Filipino rivals Kate Lagman and Maria Margarita Delos Reyes, both clocked 44:25 to finish just ahead of her.
"It was my dream to compete in an international triathlon competition. Now that I have taken the first steps, I am getting closer to the Commonwealth Games and the 2016 Olympics. I want to represent India in these competitions," said Swapnali on her return to Mumbai.
"It was my first time and it was very good to finish sixth amongst the girls who were two years older than me. I encountered many new experiences and learnt a lot of lessons. I will work harder and will never stop participating in such competitions," she added.
The event, which attracted around 430 participants from 15 countries, is recognised by the International Triathlon Union and Asian Triathlon Confederation and was organised by the Triathlon Association of the Philippines.